Target AFR's for Idle/Cruise/Acceleration & WOT
 

I have only recently started using a wide band to tune and have been somewhat dissapointed in the lack of any guidelines to use for tuning. I understand that the only way to really know what your engine "wants" is to measure the performance. But in the real world this is more difficult than it sounds. It's hard to find a lonely stretch of flat road that you can tune on multiple times a day, for example.

After much discussion and a lot of reading and searching, not to mention the tuning and testing I have done so far, I have decided to post what I "think" target AFR should be. I am not saying these numbers are the best for all combos but seem to be working for me so far. These would be the starting points or targets when getting a tune worked out. Please feel free to chime in and tell me if I am wrong. I am hoping to come to some concincus here with fellow tuners.

BTW I have a fairly mild 5.7 HSR non-emission legal combo so 14.7 is not the golden rule here. No cat.

Idle; 14.7 to 16.5 seems to idle fine. BLM's good and plugs look ok. I "like" to see ~15.0

Steady cruise; 14.3 to 14.7 seems to be good. BLM's good. The closed loop seems to keep it at this range anyway.

Light acceleration; 13.7 to 14.2 seems to give good response. BLM's good. I add a fair amount of AE to keep it from spiking high on tip in.

Hard acceleration- not in PE; 13.3 to 13.8 seems good. Even though I am still in closed loop I have somehow got it to go a little richer. BLM's still in order at this point.

WOT; 12.0 to 12.8 is what I have been getting. Have not gone past about 4K RPM yet but feel ~12.5 should be the target. BLMs not in play. Should <12.5 be used to stay safe(R)?

Again, this is just a starting point and I welcome comments/suggestions and posts regarding what AFRs you have measured, used or believe would work best under these conditions.

Re: Target AFR's for Idle/Cruise/Acceleration & WOT
 

For natural aspirated car those are good starting points. Bigger the cam, theres potential it may want more fuel at low speeds low loads but thats where you need to experiment

Re: Target AFR's for Idle/Cruise/Acceleration & WOT
 

What is easier to tune PT, going off the BLM's or basing it off the 02's only. Also, where is your WB 02 mounted, on one exhaust mani or on the y pipe where the exhaust come together?

Sorry to hijack.

Re: Target AFR's for Idle/Cruise/Acceleration & WOT
 

No prob.

My WB is in the Y pipe just before where the cat used to be. Still use the NB for ecm. I do have to "adjust" my thinking when viewing transition afr's in that there is a slight delay between a tp change to seeing the reaction in the wb data.

For tuning I use both the WB data and blm's. I use the wb to see changes in more "real time" but still look back to blm for confirmation. It is easier for me to get a feel for "how much" of a change to make from the blm. 129-130 I may not touch. 132 needs a tich. 140 is lean. I also watch int for transitional data. But I am still new to WB use so keep that in mind. I guess I don't fully trust the wb enough to ignore the rest.

Re: Target AFR's for Idle/Cruise/Acceleration & WOT
 

I am in CL at part throttle. Im am at stoich at a lambda of approx 1.02(a tad lean of stoich). I run E10. However I have hyway enabled(>65 mph) and I am leaner at 1.09.